Extract, PM, All Grain?
If the reading is correct it will be lower alcohol and hiugher bitterness.
Chance are you got your sample from a stratified layer after adding top off water and the dilution is the result. Kind of like black and tan. The heavy stuff is at the bottom, the light stuff floats on the top. somewhere in the middle it's homogenous.
Next time, stir vigorously, sample, then pitch yeast.
If it was AG, then your sparge may have been off.